Circuit interrupting device



Oct. 3, 1950 R. H. EARLE 2,524,101

CIRCUIT INTERRUPTING DEVICE Filed Sept. 10, 1945 Patented Oct. 3, 1950 `CIRCUIT INTERRUPTING DEVICE Ralph H. Earle, Wauwatosa, Wis., assigner to McGraw Electric Company, a corporation of Delaware Application'september l0, 1945, Serial No. 615,365

6 Claims.

This invention relates to improvements in a circuit interrupting device for protective apparatus in electric distribution circuits.

Protective apparatus in common use on electric distribution lines comprises a so-calledvalve type lightning arrester including an air gap and silicon carbide or similar valve material in series relation between a distribution line and ground. Its purpose is to clear the line of abnormal surges and to interrupt the grounded circuit therethrough after the line has been cleared of the' abnormal conditions.

Protective apparatus is thus frequently subjected to very severe conditions which damage the valve material and render it inadequate to perform its function as a resistor to the ilow of current normally generated in the line and causes lock-out of protective switching equipment.

An object of this invention is to provide an improved circuit interrupting device which will interrupt the iiow of current to ground when the protective apparatus fails, but prior to interruption of the line circuit by the protective switching equipment.

The prior art suggests several ways of interrupting grounded circuits through damaged protective apparatus. closed in the patent to Earle, No. 2,315,320, issued March 30, 1943, for Automatic Circuit Interrupting Devices.

A more specific object of my invention is to provide for a lightning arrester a circuit interrupting device which embodies, in series, an air gap, a fusible joint, and a fuse Wire, the arrangement being such that the fusible joint will ordinarily melt, upon failure of the arrester on small fault currents, and the fuse wire will remain intact; while on heavy fault currents the fuse wire will melt before the fusible joint is melted.

Additionally, it is an object to provide a circuit interrupting device for lightning arresters which will introduce a gap between the arrester and ground, will operate independently of ground connections, serves as an indicator of the condition of the arrester, is simple in construction and to assemble, is easily calibrated to function under predetermined conditions, and introduces an arc extinguishing gas into the path of an arc formed by the operation of the interrupting device.

Fig. 1 is a sectional View in side elevation of my interrupter as applied to an arrester.

Fig. 2 is a View similar to Fig. l, illustrating the arrangement following operation of the interrupter.

Fig. 3 is a Sectional view taken on the line 3--3 One which is in wide use is dis- Y of Fig. l, showing a cross section of the interrupter.

Fig. 4 is a fragmentary view in vertical section illustrating a modified form of this invention.

The arrester illustrated in the drawings and more fully described in Patent No. 2,315,320 cornprises a housing I enclosing an air gap 2 and valve material 3 such as silicon carbide. A conductor 4 extends beneath the housing cap 5 and isr electrically connected with the metal closure 6. The lower end of the arrester is provided with an electrode plate 'I having centrally located threaded stud 8 projecting through the bottom of the housing. y Y j The interrupter comprises a connector cap 9 threaded on the stud and clamping a resilient washer I5 to the bottom of the housing I, an insulating sleeve IIthreaded into the cap 9 and recessed at E2 beneath the stud 8, a terminal I3 threaded on the lower end of the sleeve I I, closure I4 having an insulating guard I5, a link comprising an electrode button I6 seated in the recess i2, a strain wire Il secured in the recessed end i8 of the button I6 by means of solder I9 and provided with an eye 29 which receives a pin 2| extending transverselyr through the closure I4. A coil spring 22 embraces the lower portion 23 of the terminal I3 and a portion of the closure I4 and is held under compression between the termin al and closure. Normally the strainwire Il is held under tension by the spring 22 acting through the closure I4.

The terminal I3V is provided with a laterally projecting clamping jaw Zi integral therewith, a movable clamping jaw 25 having spaced hookshaped clamping iingers 29 between which the jaw 24 is positioned, and a clamping bolt 2l threaded through movable jaw 25 and engaging the jaw 2li to draw the lingers 26 into clamping engagement with t-he ground wire 28. As indicated, the insulating guard I5 is recessed at 29 to accommodate the bolt 2`I and jaws 24 and 25 and to give access to the bolt for manipulation thereof.

In operation, the device functions as follows:

When a surge of excessive voltage occurs in a line to which the arrester is connected, it will pass through the conductor 4, across the gap 2, through the valve material 3, across the gap 30 between the stud 8 and button I5, and to ground through the wire I'I, closure I4, terminal I3, and ground wire 28. A circuitgto ground thus established permits generated current in the line to short circuit through the arrester to ground. When the surge current has been dissipated, the

valvematerial will normally limit the ilovv of generated current therethrough to a value which will enable air 2 to extinguish the arc therein and interrupt the circuit through the ar- -iovveveig in the event the valve material 3 is damaged while discharging the excess voltage currents that are passing through it and is then unable to perform its function adequately to restrict the dow of generated currents, the conti ed flow of small current across the gap 3D Wil heat the button i6 sufficiently to melt the solder i9 and release the strain Wire il. In the event a heavy fault current continues to ilow across the gap 35.3, the strain Wire il' will melt. In either event, the coil spring Z2 will Withdraw the wire il cy moving the closure hl and guard l downwardly. The closure and guard Will continue this movement until they reach a point where they will ce held suspended from the terminal by ins of the ilexible Wire 3i more clearly shown in 2 As the strain '-,vire il vor a portion thereof is w"tton i an arc will be drawn the arc.

In the event of failure of the arrester, either the interrupter will operate alone to extinguish the arc and interrupt the follow current or the backup fuse on the line will operate to sectionalize the arrester before the interrupter extinguishes the arc. In any event, the blown interrupter will always be a visible indication of the failure of the arrester.

Since the movable parts of the interrupter are free, after release, to move Without interference by the ground connection, it is obvious that a quick and dependable operation is assured.

In the embodiment disclosed in Fig. 4 the insulating sleeve 35 is threaded into cap 9 and is recessed at 3S beneath the stud 8. An electrode button 3l is seated in the recess 36 and a fusible Wire 38 is secured in the recessed end 39 of the button 3'! by means of solder 4D. Ground Wire 4l is joined to the fusible wire 38. The bore of sleeve 35 may be provided with a liner of gas evolving material 42.

The operation of the device disclosed in Fig. 4 is similar to that disclosed for the device illustrated in Fig. l, except that there is no coil spring to aid in the withdrawal of the ground Wire 4| which drops from the sleeve 35 because of gravity and the expulsive force of the gas evolved from the liner 42.

From the foregoing it is apparent that the novel circuit interrupter will protect a line from excessive short circuiting through a damaged arrester, will by proper calibration of its parts in no Way interfere with normal operations of the arrester, will serve as an indicator of arrester damage, is simple in construction and to assemble, and may be accurately calibrated to function upon the occurrence of given conditions within the airester.

I claim:

1. A circuit interrupting device comprising an expulsion tube, a terminal at the upper end of said expulsion tube, a fuse link Within said tube, a fusible joint connecting said fuse link and terminal, a closure member supported by said fuse link closing the lower end of said expulsion tube, an electrode spaced from said terminal to provide a gap therebetween, and spring means biasing said closure member in a direction away from said tube, the arrangement being such that the heat of an are of predetermined duration, between said terminal and electrode, is operative to sever said fusible joint and release said fuse link and said closure member.

2. A circuit interrupting device comprising in combination an insulating sleeve the inner wall of which embodies an arc extinguishing material, an electrode cap secured to said sleeve and having an electrode portion in alignment with the bore of said sleeve, said sleeve and cap jointly forming an arcing chamber, a fuse link terminal having a flange seated on said sleeve within said arcing chamber and comprising an arcing electrode spaced from said cap, said terminal having a recessed shank in said bore exteriorly of said chamber, a fuse wire in said bore extending from Within said recess, and a low melting alloy in said recess securing said fuse Wire therein.

3. A circuit interrupting device comprising in combination an insulating sleeve the inner Wall of which embodies an arc extinguishing material, an electrode cap secured to said sleeve and having an electrode portion in alignment with the bore of said sleeve, said sleeve and cap jointly forming an arcing chamber, a fuse link terminal having a ilange seated on said sleeve within said arcing chamber and comprising an arcing electrode spaced from said cap, said terminal having a recessed shank in said bore exteriorly of said chamber, a fuse wire in said bore extending from Within said recess, a low melting alloy in said recess securing said fuse wire therein, and a conductor connected to said fuse Wire and extending from said sleeve.

4. A circuit interrupting device comprising in combination an insulating sleeve the inner wall of Which embodies an arc extinguishing material, an electrode cap secured to said sleeve and having an electrode portion in alignment with the bore of said sleeve, said sleeve and cap jointly forming an arcing chamber, a fuse link terminal having a flange seated on said sleeve within said arcing chamber and comprising an arcing electrode spaced from said cap, said terminal having a recessed shank in said bore exteriorly of said chamber, a fuse wire in said bore extending from within said recess, a low melting alloy in said recess securing said fuse Wire therein, and a closure member at the end of said sleeve opposite said cap, said member secured to said link and being electrically conductive.

5. A circuit interrupting device comprising in combination an insulating sleeve the inner Wall of which embodies an arc extinguishing material, an electrode cap secured to said sleeve and having an electrode portion in alignment With the bore of said sleeve, said sleeve and cap jointly forming an arcing chamber, a fuse link terminal having a flange seated on said sleeve within said arcing chamber and comprising an arcing electrode spaced from said cap, said terminal having a recessed shank in said bore exteriorly of said chamber, a fuse Wire in said bore extending from within said recess, a low melting alloy in said recess securing said fuse wire therein, a closure member at the end of said sleeve opposite said cap, said member secured to said link and being electrically conductive, and a terminal on said sleeve adjacent said closure member including a conductor clamp electrically connected with said closure member.

6. A circuit interrupting device comprising in 'ni-icombination an insulating sleeve the inner Wall of which embodies an arc extinguishing material, an electrode cap secured to said sleeve and having an electrode portion in alignment with the bore of said sleeve, said sleeve and cap jointly forming an arcing chamber, a fuse link terminal having a flange seated on said sleeve within said arcing chamber and comprising an arcing electrode spaced from said cap, said terminal having a recessed shank in said bore exteriorly of said chamber, a fuse wire in said bore extending from Within said recess, a low melting alloy in said recess securing said fuse Wire therein, a closure member at the end of said Sleeve opposite said cap, said member secured to said link and being electrically conductive, a terminal on said sleeve adjacent said closure member including a conductor clamp electrically connected with said closure member, and spring means interposed between said closure member and terminal and placing said fuse wire under stress.

RALPH H. EARLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

